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emsec / ChameleonMini

The ChameleonMini is a versatile contactless smartcard emulator compliant to NFC. The ChameleonMini was developed by https://kasper-oswald.de. The device is available at https://shop.kasper.it. For further information see the Getting Started Page https://rawgit.com/emsec/ChameleonMini/master/Doc/Doxygen/html/_page__getting_started.html or the Wiki tab above.
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BOM correction (for selfmade hw) #260

Closed robots closed 4 years ago

robots commented 4 years ago

Hi, for all of you guys who made Chameleon Mini on their own here is little advice:

Capacitors C29 and C30 should be 47pF.

This tunes the mismatch between transmitter and antenna. It increases reader distance from -1 to about 2-3cm. RSSI without tag changes from 500-600 to ~2500mV.

More about this here: https://my.eng.utah.edu/~mlewis/ref/NFC/AN1445.pdf

timokasper commented 4 years ago

Hi robots, Thanks for the advice, but I cannot recommend to follow your advice. The RSSI without tag, with exactly the components of the BOM, should be more than 10V - all of the ChameleonMini RevG sold in the webshop of Kasper&Oswald have to pass this test! It seems that you have made some other mistake during manufacture. I have spent about a week for fine-tuning the antenna matching both for emulation and reader operation of Rev.G, before we had several thousand devices produced after the kickstarter project... and changing the value of a single (or even 2) capacitors affected all capabilities (sniffing, reading, emulating, ...) it was a tidious try-and-improve approach and I think we have found a good compromise for the tuning.... anyway, 2500mV is definitely not enough, there is s.th. wring with your device.

robots commented 4 years ago

Well, its been 2years since i made the board. I dont remember what parts were ordered, but it could be problem on my side :-) I will replace all RF frontend parts just to be sure.

libin-ka commented 4 years ago

What is the capacitance value of C29 C30

robots commented 4 years ago

these capacitors are not populated in BOM

libin-ka commented 4 years ago

See pictures c29 and c30 in the wiki https://github.com/emsec/ChameleonMini/wiki